Interlock clip means



p 11, 1962 w. H. EDMUNDS 3,054,025

INTERLOCK CLIP MEANS Filed Jan. 26, 1959 2 Sheets-Sheet 1 United States Patent 3,il54,tl25 ENTERLUCK CLIP MEANS Wiiiiarn Harold Edmnnds, Havertown, lla., assignor to T-T-E Circuit Breaker Company, Philadelphia, Pa, a corporation of Pennsyivania Filed inn. 2.6, H59, Ser. No. 739,214- 4 Claims. (Ci. 350 419) The instant invention relates generally to interlock lock means and more particularly to means which provides non-interchangeability for circuit breakers.

Circuit breakers which are utilized for protecting branch circuits in the average home, regardless of their current ratings, are usually provided with identical casings. Thus, a circuit breaker of low rating, say 15-2O amperes may readily be removed from the panelboard and easily be replaced by the home owner with a circuit breaker of a high rating, say 30-50 amperes. Now the branch circuit in question is not adequately protected and as a result there is great danger of fire. Thus, it is neccessary to provide an interlock means to prevent interchangeability between circuit breakers of different ratings which are encased in the same size housings.

It is desirable that the following feature be incorporated in the non-interchangeability means.

(1) The non-interchangeability means should minimize the amount of work required for the contractor or assembler installing the circuit breakers in the panelboard.

(2) The non-interchangeability means must be such that circuit breakers having this feature can still be used in panelboards now in the field without alteration to the pane'lboard.

(3) Provisions must be included for spare circuits in the panelboard with these spares being adapted to accommodate only circuit breakers of low ampere ratings. However, any authorized electrician should be able to alter the panelboard so that circuit breakers of higher ratings may be installed as required.

(4) The non-interchangeability means for the circuit breakers should be such that the user or householder can readily replace a circuit breaker of the same rating class if necessary. This would then make the circuit breaker replaceable as in the case of fuses.

(5 The cost of the non-interchangeability feature must be maintained at a minimum.

The non-interchangeability means is especially adapted for panelboards in which male stabs are mounted on the main bus bars as shown in copending application (C- 536) Serial No. 626,442 filed December 5, 1956 in the name of William Harold Edmunds, entitled Selective Mounting for Circuit Interrupters, and assigned to the assignee of the instant invention. The circuit breaker for this type of panelboard is of a type whose line terminal comprises a female stab in the form of a clip which engages the male stab.

The non-interchangeability means comprises a member or clip, of elongated U-shaped cross-section, which is forced on the male stab of the panel board and is adapted to be captivated thereby. This is achieved by providing the clip with ears which are inwardly extending and providing the panelboard stabs with holes which receive the inwardly extending ears to retain the clips to the stabs. Thus, the clips cannot readily be removed from the stabs without considerable effort and it is extremely doubtful as to whether the members can be removed without first deenergizing the panelboard.

The circuit breakers of low current rating are provided with female connectors having wide openings which can accommodate the stabs having clips mounted thereon while the circuit breakers of high current rating are provided with female terminals whose arms are so closely spaced that a stab having the member mounted thereto cannot be received by the line terminal of the circuit breaker of high current rating.

When a clip is mounted to the stabs of the panelboard it is highly unlikely that the clip will be removed by an untrained person since it is connected to an energized bus. Further, the manner in which the clip is captivated by the stab makes the convenient removal of the clip possible only by utilizing a special tool.

The clip is adapted to be inserted at the factory in the female type line terminals of the circuit breakers of low current rating. Then it is only necessary for the assembler to swing the circuit breaker in place over the male stab and when the circuit breaker is removed from the panelboard for replacement the clip is captivated by the male stab. While the clips are captivated by the male stabs these same clips may readily be removed from the female stabs of the circuit breakers. It is necessary to remove the clip from a circuit breaker when it is being mated with a panelboard male stab which has a captivated clip mounted thereon.

For the spare circuits, where spaces have been left in the panelboard for future circuit breakers, a clip is added directly to the male stab by the assembler. Thus, if the householder decides to wire in an additional circuit, only circuit breakers of low current rating can be installed in the spare circuits.

Circuit breakers of low current rating having female terminals with widely spaced arms may still be mounted to panelboards presently in the field whose male stabs do not have the holes required to captivate the clips. The clips are formed of conducting spring material, preferably of a copper alloy, and the inwardly extending ears are pierced from the spring material forming the arms of the elongated U. Thus, the cars will be forced outward when the clip is installed on a stab not having an appropriately positioned opening for the reception of the ears. When the circuit breaker is being removed the clip ears will bite into the male stab thereby retaining the clip to the stab so that this panelboard circuit will not accept a circuit breaker of high current rating.

Some panelboards are contsructed to receive circuit breakers having wide housings and as a result the male stabs are widely spaced. With panelboards of this construction, it often becomes desirable to replace a single wide breaker with two narrow breakers which will protect two independent low current capacity circuits.

The panelboard may be conveniently altered to accommodate two narrow circuit breakers in place of a single wide circuit breaker by utilizing a clip constructed in accordance with the principles previously outlined. This clip comprises an inverted elongated U-shaped center section having inwardly extending pierced ears which are received by a suitably positioned opening in the male to thereby captivate the clip to the stab. The clip further comprises two outside arms which extend upwardly from the bottom end of the center section and parallel to the n9 U-arms of the center section. These outside arms provide two stabs which cooperate with the female stabs of two narrow circuit breakers.

Accordingly, a primary object of the instant invention is to provide a novel means to prevent the replacement of a circuit breaker of low current rating by a circuit breaker of high current rating through inadvertance or lack of understanding on the part of the person making the replacement.

Another object is to provide a clip means which is captivated by the bus bars of a panelboard.

Still another object is to provide an interlock clip means which is readily installed in an energized panelboard.

A further object is to provide an interlock clip means which is automatically installed in the circuit with the installation of a circuit breaker in that circuit.

A still further object is to provide a novel interlock clip means which may be installed in existing panelboards as well as panelboards especially constructed therefor.

These as well as other objects of the instant invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a perspective view of a panelboard constructed in accordance with the teachings of the instant invention.

FIGURES 2A and 2B are perspective views of circuit breakers having low and high current ratings, respectively.

FIGURE 3 is a perspective view of the panelboard of FIGURE 1 showing the manner in which a circuit breaker of low current rating is mated to a stab having an interlock clip mounted thereon and also show the manner in which a circuit breaker of high current rating cannot be mounted to a stab having an interlock clip mounted thereon.

FIGURE 4 is a side elevation of an interlock clip mounted to a male stab.

FIGURE 5 is a cross-section of FIGURE 4 taken through line 5-5 looking in the direction of the arrows.

FIGURE 6 is a perspective view of a female stab type circuit breaker line terminal.

FIGURES 7A and 7B are an end view and a front elevation, respectively, of a modified form of interlock clip.

FIGURE 7C is an end view of a modified interlock clip whose front elevation is illustrated in FIGURE 7B.

FIGURE 8 is an end view of a clip which provides two male stabs in place of a single male stab.

Now referring to the figures and more particularly to FIGURES 1-6, the interlock clip 10 of the instant invention is adapted for mounting directly to the male stabs 31a, 31b of panelboard 30 which i generally of the type described in detail in US. Patent No. 2,737,613 to M. A. Morris, entitled Panel Board Terminal Mounting Blocks," issued March 6, 1956, and assigned to the assignee of the instant invention.

Briefly, panelboard 30 comprises two parallel bus bars 3 2, 33 mounted in spaced apart insulating relationship "by means of insulating block 34 and secured thereto by means of screws 35. Male stabs 31a are electrically connected to bus bar 32 while male stab 31b is electrically connected to bus bar 33. Male stabs 31a, 3112 are mounted in operative position by mounting block 34.

Circuit breaker mounting ledges 36, 37 are secured to the upwardly turned edges 38, 39, respectively of metallic frame 40. A protrusion 41 of mounting block 34- is received by an aperture 42 in mounting ledge '37 to thereby secure mounting .block 34, as well as the bus bars 32, 33 and male stabs 31a, 31b, in fixed mechanical relationship with respect to frame 40. A sheet of insulating material 43 is interposed between mounting block 34 and frame 40.

Each of the male stabs 31a, 31b are constructed in a similar manner so that only stab 31a will be described, it being understood that stab 31b is identical thereto. Stab 31a is comprised of conducting sheet material substantially rectangular in shape with the top edge thereof being provided with two undercut notches 44, for a purpose to be hereinafter explained. Stab 31a is also provided with two apertures 45 extending therethrough an positioned below notches 44, also for a purpose to be hereinafter explained.

Interlock clip 10, as best seen in FIGURES 4 and 5, is a member constructed of electrically conducting spring material having a generally U-shaped cross-section with elongated arms 11a, 11b joined by web 12. Each of the arms 11a, 11b is pierced to form inwardly extending ears 13a, 13b, respectively. Ears 13a, 13b also extend up wardly toward web 12 for a reason which shall become apparent.

Interlock clip 10 is adapted to be mounted to male stab 31a with aperture 45 being operatively positioned to receive both of the inwardly extending ears 13a, 1311 with web 12 being disposed within undercut 44. The cooperation of cars 13a, 13b and aperture 45 enables interlock clip 10 to be captivated by male stab 31a.

When male interlock clip 10 is captivated by male stab 31a, clip 10 may nevertheless be removed by spreading arms 11a, 11b. However, removal is extremely inconvenient so that it is highly unlikely than an unauthorized person would remove clip 10 from stab 31a. That is, the nature of the spring material forming clip 10 causes arms 11a, 11b to firmly grasp the sides of stab 31a so that the simultaneous spreading of arms 11a, 1112 can only be accomplished by an especially designed tool or else by two individual knife blades. Because of the close quarters existing in the panelboard when most of the circuit locations thereof are occupied by circuit breakers, the utilization of the two blade removal method is extremely cumbersome, if not impossible, at that time. Further, removal of clip 16 from a live stab 31a without utilizing a specially designed tool is highly unlikely and deenergizing panelboard 30 in order to accomplish the removal of clip M is highly undesirable.

Each of the stabs 31a, 31b are adapted to be contacted by the line terminals of two circuit breakers so that it can be said that each of the stabs 31a, 311; provides two circuit locations. When a circuit location is provided with an interlock clip 10 the insertion of a circuit breaker of high current rating is impossible since circuit breaker 50 (FIGURE 2b) is provided with a female clip type line terminal 51. The arms of terminal 51 are spaced apart by the distance A and can be spread apart only to a distance slightly greater than the thickness B of stab 31a but not as far apart as distance C which is the combined thickness of stab 31a plus interlock clip arms 11a, 11b. Thus, as best seen in FIGURE 3, circuit breaker 50 of high current rating cannot be mounted to a circuit location having interlock clip 10 mounted thereto.

However, circuit breaker of low current rating, whose housing 69 is the same size as housing 59 of circuit breaker 50, is provided with female clip type line terminal 61 whoe arms 62, 63 are separated by distance D and may be spread apart to a distance slightly exceeding distance C. Thus, circuit breaker 60 of low current rating may be inserted in a panelbord circuit which Will not accept circuit breakers 50 of high current rating even though both circuit breakers 50 and 60 have the same size housings 59, 69.

FIGURE 6 illustrates in detail the construction of line terminal 61 of low current rating breaker 60. Terminal 61 is an inverted generally U-shaped member of conducting material whose arms 62, 63 are more closely spaced at the free ends thereof than in the region of the web 64. Stationary circuit breaker contact 65 is secured to rearward extension 66 of web 64. Contact pressure is provided by U-shaped spring 67 whose arms are in engagement with the arms 62, 63 of line terminal 61 at the closely spaced free ends thereof.

Line terminal 51 of high current circuit breaker 50 is of substantially the same construction as line terminal 61. However, the contact pressure spring (not shown) for terminal 51 may have protrusions thereon which engage suitable internal formations in the circuit breaker housing 59 to limit the separation of the arms of the terminal 51 to a distance less than the distance C.

For the convenience of installation each circuit breaker 60 of low current rating is shipped from the factory with an interlock clip inserted between the arms 62, 63 of line terminal 61. In mounting a circuit breaker 60 to a circuit, such as location 70 of male stab 310 (FIGURE 3), which is not provided with an interlock clip, it is merely necessary to locate circuit breaker 60 with respect to location 70 by entering mounting protrusions 71 into a suitable recess (not shown) at the load side of the circuit breaker housing 69' and thereafter swing line terminal 61 toward stab 31a of location 70 This forces interlock clip 10 over male stab 31a and the resilient nature of clip 10 forces ears 13a, 13b outwardly with respect to their normal positions as seen in FIGURE 5 until such time as ears 13a, 13b are in alignment with stab aperture 45 at which time ears 1'30, 13b return to their normal positions.

When the circuit breaker 60 at location 70 is removed, the interlock clip 10 is captivated by stab 31a at location 70. Thus, location 70 has now been altered by interlock clip 10 so that in the normal course of events only a circuit breaker 60 of low current rating may be mounted thereto.

If a new circuit breaker 60 of low current rating is to be mounted to a panelboard circuit location having an interlock clip 10, this condition will become apparent to the installer of the circuit breaker since the arms 62, 63 of line terminals 61 cannot be spread apart a distance sufficient to accommodate two interlock clips 10 plus the thickness of stab 310. In this event, the interlock clip 10 carried by circuit breaker 60 may readily be removed from terminal 61 and thereafter the insertion of circuit breaker 60, without interlock clip 10, is made in the usual manner.

Interlock clip 10 may be installed on panel board stabs which do not have apertures 45 and undercuts 44. That is, as a circuit breaker 60 is mounted to a panelboard which is not especially adapted to utilize interlock clips 10 then the inwardly extending ears 13a, 13b of interlock clip 10 will be forced outwardly as the clip 10 is introduced to the stab. Clip arms 11a, 11b will nevertheless be in good electrical contact with the male stab. When circuit breaker 60 is thereafter removed clip 10 will nevertheless remain on the stab since ears 13a, 13b are self biased inwardly and the sharp edges 19a, 19b, respectively, thereof will dig into the stab so as to effectively maintain clip 10 to the stab.

FIGURES 7A and 7B illustrate a modification of interlock clip 10 previously described. Interlock clip 80 is also constructed of electrical conducting spring material and is comprised of a generally U-shaped elongated crosssection. The free ends of arms 81, 82 are inwardly turned to form ears 83, 84, respectively, which are positioned to be entered into a stab opening 45, when web 85 is disposed within a stab undercut 44, to thereby enable clip 80 to be captivated by the stab.

In the substantially U-shaped interlock clip 100 of FIG- URE 7C the free ends of arms 101, 102 are inwardly turned and bent back on themselves to form ears 103, 104, respectively, which are positioned to be received by stab opening 45 when web 105 is disposed within stab undercut 44.

FIGURE 8 illustrates an embodiment of my invention wherein the teachings thereof hereinbefore described are utilized to construct an adapter clip 86 which readily transforms a single circuit location provided by stab 87 into two circuit locations. Stabs 87 are spaced apart by approximately the distance between stabs 31a, 31b with an insulating barrier 88 interposed therebetween for improved electrical leakage clearance.

Adapter 86 comprises a single section 87 which is of a construction identical to that of interlock clip 10. Adapter 86 also includes two side sections 90, 91 which extend upwardly from the lower ends of the center section arms 92, 93, respectively and are substantially parallel thereto. Thus, circuit adapter '86 is mounted to stab 87 with inwardly extending ears 94, 95 entered into stab aperture 96 so that adapter 86 is captivated by stab 87. Now side sections 90, 91 are positioned to act as male stabs which are engageable by the female clip type line terminals 97 of a low current rating circuit breaker 98 whose housing is approximately one half the width of either circuit breaker housing 59 or 60. Thus, the single circuit location of stab 87 has been transformed into two circuit locations 91.

Thus, the instant invention provides an interlock clip means to prevent the interchangeability of circuit breakers of high current rating for circuit breakers of low current rating even though both the low and high current rating circuit breakers have the same size housings.

The interlock means is constructed to automatically be mounted to the panelboard with the mounting of the circuit breaker of low current rating to be captivated by the stab of the panelboard so that upon removal of the circuit breaker of low current rating the interlock clip means remains mounted to the stab. This prevents the mounting of a circuit breaker of high current rating in place of a circuit breaker of low current rating. Further, the interlock clip means is constructed to permit installation to panelboards presently in the field without any modifications thereto.

Although I have here described preferred embodiment of my novel invention, many variations and modifications will now be apparent to those skilled in the art, and I therefore prefer to be limited, not by the specific disclosure herein, but only by the appending claims.

I claim:

1. An interlock clip means for preventing the replacement of a circuit breaker of low current rating with a circuit breaker of high current rating even though both of said circuit breakers have the same size casings; said means being constructed for removable mounting to a bus bar of a panelboard; said means being constructed to be carried by said circuit breaker of low current rating and to automatically be mounted to said bus bar upon mounting of said circuit breaker of low current rating to said panelboard; said means being captivated by said bus bar after mounting thereon; said means comprising a clip constructed of spring material; said clip being of an elongated U-shaped cross-section having a first means extending inwardly from at least one of the arms thereof; said first means also extending toward the web of said elongated U-shaped cross-section.

2. The combination comprising a circuit breaker including a terminal and a clip means removably mounted to said terminal; said clip means being operatively positioned to engage a bus bar of a panelboard when said circuit breaker is mounted to said panelboard; said clip means being constructed to remain in engagement with said bus bar when, thereafter, said circuit breaker is removed from said panel-board; said means comprising a clip constructed of spring material; said clip being of an elongated U-shaped cross-section having a first means extending inwardly from at least one of the arms thereof; said first means also extending toward the web of said elongated U-shaped cross section.

3. A panelboard comprising a plurality of elongated bus bars, a first means insulating said bus bars from one another, and at least one interlock means mounted to at least one of said bus bars at a first location; said interlock means being constructed to permit a circuit breaker of low current rating to be mounted to said panelboard at said first location and to prevent a circuit breaker of high current rating to be mounted to said panelboard at said first location even though both of said circuit breakers have the same size casings; said interlock means comprising a clip constructed of spring material; said clip being of an elongated U-shape cross-section having projections inwardly extending from the arms of the U-shape; a male stab at said first location connected to one of said bus bars; said stab having an opening wherein said projections are disposed to thereby captivate said clip; said stab having an undercut wherein the web of the U-shape is disposed,

4. A clip means adapted to be mounted to a male stab of a panelboard; said clip means being constructed of spring material and comprising an inverted elongated U-shaped center section and two side sections; said side sections extending upwardly from the lower ends of the arms of said center section and being substantially parallel to said arms; said arms having inwardly extending portions adapted to be received by an opening in said stab for captivating said clip means.

References Cited in the file of this patent UNITED STATES PATENTS 

